This invention is directed to blends of a poly(amide imide) and a poly(aryl ether ketone) and, optionally, a poly(arylene sulfide). These blends exhibit improved solvent resistance and hydrolytic stability.
Electrical connectors, in many applications, require high solvent resistance, dimensional stability, and ultimate use temperature. The material traditionally used in such applications is peroxide cured diallyl phthalate, which is a thermoset resin. Consequently, it cannot be processed by injection molding. Additionally, in some electrical connector applications, a poly(amide imide), hereinafter called "PAI", has been used.
Illustrative of these PAI's are polymers represented by repeating units of the formula: ##STR1## wherein R is selected from ##STR2## wherein R.sub.1 is selected from O, --CO, S, alkylidene containing from 1 to about 10 carbon atoms, Ar is selected from ##STR3## and n is an integer of from 0.05 to 25.
Also included are PAI copolymers having reocurring units of: ##STR4## wherein one carbonyl is meta to and one carbonyl is para to each amide group wherein, Z is a trivalent aromatic moiety containing 1 to 4 benzene rings or lower-alkyl-substituted benzene rings, R.sub.2 and R.sub.3 are different and are divalent wholly- or largely-aromatic hydrocarbon radicals. These hydrocarbon radicals may be a divalent aromatic hydrocarbon radical of from 6 to about 10 carbon atoms, or two divalent aromatic hydrocarbon radicals of from 6 to about 10 carbon atoms joined directly or by stable linkages such as --O--, methylene, --CO--, --SO.sub.2 --, --S--; for example, --R'--O--R'--, --R'--CH.sub.2 --R'--, --R'--CO--R'--, --R'--SO.sub.2 --R'-- and --R'--S--R'--, wherein R' is the said divalent aromatic hydrocarbon radical. By lower alkyl is meant an aliphatic radical of from 1 to about 6 carbon atoms.
Preferably the copolymers have reocurring units of the formula ##STR5## wherein R.sub.3 and R.sub.4 are different and are chosen from the class consisting of: ##STR6##
These PAIs are well known in the art and are prepared as described in, for example, U.S. Pat. Nos. 3,659,938, 3,988,374 and 4,016,140. Some of them are commercially available and sold under the trademark "Torlon" (Amoco Chemicals Corp. Chicago, Ill.).
Poly(amide imide)s have a high glass transition temperature (Tg) (&gt;265.degree. C.), excellent creep resistance and are able to meet the other requirements needed for high performance electrical connectors. However, PAIs are attacked by some solvents, such as pyridine at elevated temperatures and also they are hydrolyzed by bases. Further, articles molded from poly(amide imide) resins must undergo a prolonged curing process to develop high strength and impact resistance. For example, articles molded from a commercially available poly(amide imide), e.g., Torlon 4203L (obtained from Amoco Chemicals) are recommended to be cured in a circulating oven for 24 hours at 165.degree. C., 24 hours at 245.degree. C., and 24 hours at 260.degree. C. Proceeding from one temperature to a higher temperature too quickly results in distorted and foamed parts.
As obviously desirable as such resins may be in some properties, it clearly would be desirable to be able to make molded products from them which possess increased solvent resistance and shorter cure times.
It has now been found that the combination of a poly(aryl ether ketone) hereinafter called "PAEK" and, optionally, a poly(arylene sulfide) hereinafter called "PAS", with a poly(amide imide) results in molded products having improved solvent resistance and much shorter cure times. A special bonus is improved hydrolytic stability over that possessed by PAI's. On the other hand, the combination yields molded products with improved strength, notched Izod toughness and heat deflection temperature over that provided by PAEK's alone and PAS alone. In this respect, the product retains the properties of the PAI.